A direct view storage tube normally comprises a foraminous storage grid, an electron gun for writing information onto said storage grid, a flood electron gun for reading and erasing information on said storage grid and a phosphor display screen for said information. The write gun writes a positive charge corresponding to the electrical input information onto the storage grid. The flood gun, which provides a beam which floods the entire storage grid, is operated at a suitable potential during the read operation so that electrons pass through the foraminous storage grid and excite the phosphor screen to provide a light image corresponding to the charge information written on the storage grid. In this manner, a visual display is formed. The display is erased by charging the storage grid sufficiently negative to prevent the passage of the viewing beam electron from the flood gun. This is normally accomplished by applying a positive pulse to the backplate of the storage grid thereby causing the viewing beam electrons to collect on the insulating coating on the storage grid.
Brightness, contrast and resolution are problems that face designers of electronic tubes in this area. In U.S. Pat. No. 3,088,048 by Ogland et al, a storage display tube is described in which an additional control grid is provided between the storage grid and the phosphor screen. This patent describes a technique associated with such a control grid to suppress electron bombardment of the phosphor display screen during the erase cycle and thereby suppress the generation of light flashes from the screen that may arise during the erase cycle. By this technique, one is able to further enhance the capability of the storage display tube as far as viewing a scene in bright ambient light conditions. The structure described in the Ogland et al patent results in a slight loss in the brightness in comparison with a conventional storage tube wherein no suppressor grid is provided between the storage grid and the phosphor screen. The brightness in all display tubes is presently limited by the flood gun cathode current made available to the display screen through the storage assembly.